Semiconductor structures with deep trench capacitor and methods of manufacture

ABSTRACT

An integrated FinFET and deep trench capacitor structure and methods of manufacture are disclosed. The method includes forming at least one deep trench capacitor in a silicon on insulator (SOI) substrate. The method further includes simultaneously forming polysilicon fins from material of the at least one deep trench capacitor and SOI fins from the SOI substrate. The method further includes forming an insulator layer on the polysilicon fins. The method further includes forming gate structures over the SOI fins and the insulator layer on the polysilicon fins.

FIELD OF THE INVENTION

The invention relates to semiconductor structures and methods ofmanufacture and, more particularly, to an integrated FinFET and deeptrench capacitor structure and methods of manufacture.

BACKGROUND

FinFETs are three dimensional structures which provide excellentscalability. For example, FinFETs rise above the planar substrate,giving them more volume than conventional gate structures. Also, bywrapping the gate around the channel, little current is allowed to leakthrough the body when the device is in the off state, i.e., therebyproviding low gate leakage current. This provides superior performancecharacteristics, e.g., lower threshold voltages, resulting in improvedswitching speeds and power.

FinFETs can be fabricated using, for example, silicon on insulator (SOI)substrates. In SOI technologies, FinFETs can be used with many otherdevices and structures, and can be fabricated using CMOS technologies,e.g., lithography, etching and deposition methods. However because ofthe three dimensional structure, integration with other devices and/orstructures are difficult and quite challenging.

SUMMARY

In an aspect of the invention, a method comprises forming at least onedeep trench capacitor in a silicon on insulator (SOI) substrate. Themethod further comprises simultaneously forming polysilicon fins frommaterial of the at least one deep trench capacitor and SOI fins from theSOI substrate. The method further comprises forming an insulator layeron the polysilicon fins. The method further comprises forming gatestructures over the SOI fins and the insulator layer on the polysiliconfins.

In an aspect of the invention, a method comprises forming deep trenchcapacitors in an SOI substrate. The method further comprises forming SOIfins from the SOI substrate. The method further comprises formingpolysilicon fins from the deep trench capacitors. The method furthercomprises patterning the SOI fins such that ends of the SOI fins are incontact with the polysilicon. The method further comprises forming aninsulator material on the polysilicon fins. The method further comprisesforming gate structures on the SOI fins and the insulator material. Themethod further comprises forming a material on exposed materials of theSOI fins and polysilicon fins to connect the SOI fins and polysiliconfins.

In an aspect of the invention, a structure comprises a plurality of deeptrench capacitors formed in a silicon on insulator (SOI) substrate, eachof the plurality of deep trench capacitors having a fin structure. Thestructure further comprises a plurality of SOI fins each of which havingends in contact with respective fin structures of the deep trenchcapacitors. The structure further comprises an insulator material on thefin structures of the plurality of deep trench capacitors. The structurefurther comprises a gate structure extending over the insulator materialand the SOI fins.

In another aspect of the invention, a design structure tangibly embodiedin a machine readable storage medium for designing, manufacturing, ortesting an integrated circuit is provided. The design structurecomprises the structures of the present invention. In furtherembodiments, a hardware description language (HDL) design structureencoded on a machine-readable data storage medium comprises elementsthat when processed in a computer-aided design system generates amachine-executable representation of the integrated FinFET and deeptrench capacitor structure, which comprises the structures of thepresent invention. In still further embodiments, a method in acomputer-aided design system is provided for generating a functionaldesign model of the integrated FinFET and deep trench capacitorstructure. The method comprises generating a functional representationof the structural elements of the integrated FinFET and deep trenchcapacitor structure.

In embodiments, a method in a computer-aided design system generates afunctional design model of an integrated FinFET and deep trenchcapacitor structure. The method comprises: generating a functionalrepresentation of a plurality of deep trench capacitors formed in asilicon on insulator (SOI) substrate, each of the plurality of deeptrench capacitors having a fin structure; generating a functionalrepresentation of a plurality of SOI fins each of which having ends incontact with respective fin structures of the deep trench capacitors;generating a functional representation of an insulator material on thefin structures of the plurality of deep trench capacitors; andgenerating a functional representation of a gate structure extendingover the insulator material and the SOI fins.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is described in the detailed description whichfollows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.

FIGS. 1-11 show fabrication processes and respective structures inaccordance with aspects of the present invention; and

FIG. 12 is a flow diagram of a design process used in semiconductordesign, manufacture, and/or test.

DETAILED DESCRIPTION

The invention relates to semiconductor structures and methods ofmanufacture and, more particularly, to an integrated FinFET and deeptrench capacitor structure and methods of manufacture. Morespecifically, the present invention comprises a method of manufacturinga robust connection between a FinFET and eDRAM semiconductor structure.By way of example, the processes of the present invention result in astructure with a robust connection between polysilicon material of theeDRAM (e.g., deep trench capacitor) and an SOI (silicon-on-insulator)fin of the FinFET, using epitaxial material. The connection between theSOI fin and polysilicon material of the eDRAM can be formed in aself-aligned process.

In more specific embodiments, the processes of the present inventionintegrate a deep trench capacitor (e.g., eDRAM) with an existing finbased CMOS process. In embodiments, the integration includes etching anSOI fin and polysilicon material (polysilicon fin) of the deep trenchcapacitor in same processes, with the connection of the SOI fin topolysilicon material (e.g., polysilicon fin of the deep trenchcapacitor) being formed in a self-aligned manner. In embodiments, thepresent invention uses a self-aligned growth process of epitaxialmaterial to robustly connect the SOI fin and polysilicon fin of the deeptrench capacitor. The epitaxial material on the polysilicon sidewalladvantageously provides a reduced strap resistance between the SOI finand polysilicon fin. In optional embodiments, the epitaxial material canbe eliminated; although, this may impact the strap resistance, it hasthe potential for reducing fin to neighboring deep trench shorts. Inembodiments, the processes of the present invention further includepatterning a trench top oxide under a passing wordline (PWL) so that PWLto deep trench capacitor shorts can be avoided.

FIG. 1 shows a structure and respective processing steps in accordancewith aspects of the present invention. More specifically, the structure5 of FIG. 1 includes a deep trench capacitor 10 formed in a SOIsubstrate 15. The SOI substrate 15 can be fabricated using anyconventional processes such as, for example, SiMOX or other knownbonding techniques. By way of illustrative example, the substrate 15includes a buried oxide layer 15 b sandwiched between a Si wafer 15 aand a semiconductor layer 15 c. In embodiments, the semiconductor layer15 c can be any semiconductor material such as, for example, Si, SiGe,Ge, GaAs, as well as other III/V or II/IV compound semiconductors or anycombinations thereof.

In embodiments, the deep trench capacitor 10 can be an eDRAM, formedusing conventional processes and materials. For example, a deep trenchis formed through the layers 15 a, 15 b and 15 c, using conventionallithography and etching processes, e.g., isotropic etching processes.The deep trench is then lined with a dielectric material 10 a, e.g.,hafnium oxide or other high-k dielectric material. In embodiments, thedielectric material 10 a can be any insulator material (not limited to ahigh-k dielectric) deposited to a thickness of about 1 nm to about 3 nm;although other thicknesses are also contemplated by the presentinvention. A metal layer 10 b, e.g., TiN, is then deposited on thedielectric material 10 a to a thickness of about 1 nm to about 3 nm;although other thicknesses are also contemplated by the presentinvention. The remaining portion of the trench is then filled withpolysilicon material 10 c. It should be understood by those of ordinaryskill in the art that deposition methods of materials 10 a, 10 b and 10c may be formed using conventional deposition processes, e.g., atomiclayer deposition (ALD).

Still referring to FIG. 1, a thin oxide material (hardmask) 20 isdeposited on the layer 15 c. The oxide material 20 can be depositedusing a conventional plasma enhanced chemical vapor deposition (PECVD)process. In embodiments, a pad nitride film (SiN) 25 is deposited on theoxide material 20. The pad nitride film 25 can be deposited using PECVDprocesses, to a thickness of about 30 nm to 80 nm; although othermaterial thicknesses are also contemplated by the present invention.

FIGS. 2-5 show a sidewall image transfer process in accordance withaspects of the present invention. More specifically, in FIG. 2, anamorphous silicon layer 30 is deposited on the pad nitride film 25. Theamorphous silicon layer 30 can be deposited using, for example, a PECVDor CVD process. In embodiments, the amorphous silicon layer 30 can bedeposited to a thickness of about 80 nm to 150 nm, and preferably about2× the thickness of the pad nitride film 25. The amorphous silicon layer30 then undergoes a lithographic and etching process to form mandrels 30a. An oxide sidewall deposition process is then performed, to form oxidesidewalls 35 on the sides of the mandrels 30 a.

In FIG. 3, the mandrels 30 a are removed, leaving the sidewalls 35. Inembodiments, the removal of the mandrels is performed using a selectiveetchant, as should be known to those of skill in the art. Inembodiments, the selective etchant can cause recesses 25 a in the padnitride film 25; although such recesses can be avoided by reducing theetch time.

In FIG. 4, an anisotropic etching process is performed to transfer thesidewall pattern of the sidewalls to the underlying pad nitride film 25.This process forms nitride fins 25 a. The sidewalls 35 are then removedusing, for example, a sidewall image transfer spacer strip of, forexample, oxide etchants with an anisotropic etching. By way of example,the oxide etchants can be an HF gas or vapor etch, or a SiCoNi, using afluorine component to etch the oxide sidewalls.

In FIG. 5, an anisotropic etching process is performed to transfer thesidewall pattern of the nitride fins 25 a to the underlying layer 15 c.This process forms SOI fins 40. This transfer etching process also formspolysilicon fins 45, contacting the SOI fins 40. The nitride fins 25 aare then removed using, for example, a hot phosphorous etchant.

FIG. 6 shows additional processing steps and a respective structure inaccordance with aspects of the present invention. More specifically, theSOI fins 40 are patterned using conventional lithography and etchingprocesses. In this patterning, ends 40 a of the SOI fins 40 remain incontact with the polysilicon fins 45. This contact will provide aconnection between the FinFET and a deep trench capacitor (eDRAM), i.e.,SOI fins 40 and polysilicon fins 45. The thin oxide material (oxidematerial 20, shown in FIG. 1) can also be removed using a dilute HF(DHF) etching process.

In FIG. 7, an oxide layer 50 is deposited on the SOI fins 40 andpolysilicon fins 45, using conventional deposition methods. Inembodiments, the oxide layer 50 can be formed using a blanket depositionof SiO₂, for example. In embodiments, the oxide layer 50 can bedeposited to a depth of about 3 nm to 6 nm; although other thicknessesare also contemplated by the present invention. In embodiments, theoxide layer 50 will provide protection to the underlying SOI fins 40from shorting with a subsequently formed conductive material.

FIGS. 8 and 9 show further processing steps and respective structures inaccordance with aspects of the present invention. In FIG. 8, a mask 55is formed over the oxide layer 50. Through conventional lithography andetching processes, the oxide layer 50 is patterned to expose the SOIfins 40. The oxide layer is then removed from over the SOI fins 40.After the oxide removal process, the mask 55 layer can be removed usingconventional oxygen ashing processes. As shown in FIGS. 8 and 9, as themask 55 remains over the polysilicon fins 45 during the oxide removalprocess, the oxide layer 50 will remain over the polysilicon fins 45after the etching process (see, FIG. 9). The oxide layer 50 will preventshorts from occurring between the polysilicon fins 45 (of the deeptrench capacitor) and a subsequently formed gate structure.

FIG. 10 shows gate formation processes in accordance with aspects of thepresent invention. Specifically, a gate dielectric material 60 isblanket deposited on the SOI fins 40 and other structures shown, forexample, in FIG. 9, e.g., over the oxide layers 15 b and 50. Inembodiments, the gate dielectric material 60 can be deposited to athickness of about 2 nm to 3 nm; although other thicknesses are alsocontemplated by the present invention. In embodiments, the gatedielectric material 60 can be a high-k dielectric material, e.g.,hafnium oxide, or other high quality dielectric material, e.g., SiO₂. Asemiconductor material 65, e.g., Si, is deposited on the gate dielectricmaterial 60. In embodiments, the semiconductor material 65 is insulatedfrom the polysilicon film 45 by the oxide material 50, therebypreventing shorts in the deep trench capacitor 10. A capping material70, e.g., Ni, is then deposited on the semiconductor material 65. Thematerials 60, 65 and 70 are then patterned using conventionallithography and etching processes, to form gate structures 75.

As shown in FIG. 11, sidewalls 80 are formed on the gate structures 75.In embodiments, the sidewalls 80 are formed by a blanket deposition ofnitride (or other spacer material, e.g., oxide), followed by ananisotropic etch to remove the material from horizontal surfaces, e.g.,over exposed portions of the fins 40, oxide material 15 b, etc. Inoptional embodiments, an epitaxial material 85 is selectively grown onthe exposed SOI fins 40 and polysilicon fins 45, to provide a robustconnection between the SOI fins 40 and the polysilicon fins 45. Inembodiments, the epitaxial material 85 is silicon, grown to a depth ofabout 15 nm to 25 nm to reduce strap resistance, thus making a morerobust connection between the SOI fins 40 and the polysilicon fins 45.

FIG. 12 is a flow diagram of a design process used in semiconductordesign, manufacture, and/or test. FIG. 12 shows a block diagram of anexemplary design flow 900 used for example, in semiconductor IC logicdesign, simulation, test, layout, and manufacture. Design flow 900includes processes, machines and/or mechanisms for processing designstructures or devices to generate logically or otherwise functionallyequivalent representations of the design structures and/or devicesdescribed above and shown in FIGS. 1-11. The design structures processedand/or generated by design flow 900 may be encoded on machine-readabletransmission or storage media to include data and/or instructions thatwhen executed or otherwise processed on a data processing systemgenerate a logically, structurally, mechanically, or otherwisefunctionally equivalent representation of hardware components, circuits,devices, or systems. Machines include, but are not limited to, anymachine used in an IC design process, such as designing, manufacturing,or simulating a circuit, component, device, or system. For example,machines may include: lithography machines, machines and/or equipmentfor generating masks (e.g. e-beam writers), computers or equipment forsimulating design structures, any apparatus used in the manufacturing ortest process, or any machines for programming functionally equivalentrepresentations of the design structures into any medium (e.g. a machinefor programming a programmable gate array).

Design flow 900 may vary depending on the type of representation beingdesigned. For example, a design flow 900 for building an applicationspecific IC (ASIC) may differ from a design flow 900 for designing astandard component or from a design flow 900 for instantiating thedesign into a programmable array, for example a programmable gate array(PGA) or a field programmable gate array (FPGA) offered by ALTERA® Inc.or XILINX® Inc.

FIG. 12 illustrates multiple such design structures including an inputdesign structure 920 that is preferably processed by a design process910. Design structure 920 may be a logical simulation design structuregenerated and processed by design process 910 to produce a logicallyequivalent functional representation of a hardware device. Designstructure 920 may also or alternatively comprise data and/or programinstructions that when processed by design process 910, generate afunctional representation of the physical structure of a hardwaredevice. Whether representing functional and/or structural designfeatures, design structure 920 may be generated using electroniccomputer-aided design (ECAD) such as implemented by a coredeveloper/designer. When encoded on a machine-readable datatransmission, gate array, or storage medium, design structure 920 may beaccessed and processed by one or more hardware and/or software moduleswithin design process 910 to simulate or otherwise functionallyrepresent an electronic component, circuit, electronic or logic module,apparatus, device, or system such as those shown in FIGS. 1-11. As such,design structure 920 may comprise files or other data structuresincluding human and/or machine-readable source code, compiledstructures, and computer-executable code structures that when processedby a design or simulation data processing system, functionally simulateor otherwise represent circuits or other levels of hardware logicdesign. Such data structures may include hardware-description language(HDL) design entities or other data structures conforming to and/orcompatible with lower-level HDL design languages such as Verilog andVHDL, and/or higher level design languages such as C or C++.

Design process 910 preferably employs and incorporates hardware and/orsoftware modules for synthesizing, translating, or otherwise processinga design/simulation functional equivalent of the components, circuits,devices, or logic structures shown in FIGS. 1-11 to generate a netlist980 which may contain design structures such as design structure 920.Netlist 980 may comprise, for example, compiled or otherwise processeddata structures representing a list of wires, discrete components, logicgates, control circuits, I/O devices, models, etc. that describes theconnections to other elements and circuits in an integrated circuitdesign. Netlist 980 may be synthesized using an iterative process inwhich netlist 980 is resynthesized one or more times depending on designspecifications and parameters for the device. As with other designstructure types described herein, netlist 980 may be recorded on amachine-readable data storage medium or programmed into a programmablegate array. The medium may be a non-volatile storage medium such as amagnetic or optical disk drive, a programmable gate array, a compactflash, or other flash memory. Additionally, or in the alternative, themedium may be a system or cache memory, buffer space, or electrically oroptically conductive devices and materials on which data packets may betransmitted and intermediately stored via the Internet, or othernetworking suitable means.

Design process 910 may include hardware and software modules forprocessing a variety of input data structure types including netlist980. Such data structure types may reside, for example, within libraryelements 930 and include a set of commonly used elements, circuits, anddevices, including models, layouts, and symbolic representations, for agiven manufacturing technology (e.g., different technology nodes, 32 nm,45 nm, 90 nm, etc.). The data structure types may further include designspecifications 940, characterization data 950, verification data 960,design rules 970, and test data files 985 which may include input testpatterns, output test results, and other testing information. Designprocess 910 may further include, for example, standard mechanical designprocesses such as stress analysis, thermal analysis, mechanical eventsimulation, process simulation for operations such as casting, molding,and die press forming, etc. One of ordinary skill in the art ofmechanical design can appreciate the extent of possible mechanicaldesign tools and applications used in design process 910 withoutdeviating from the scope and spirit of the invention. Design process 910may also include modules for performing standard circuit designprocesses such as timing analysis, verification, design rule checking,place and route operations, etc.

Design process 910 employs and incorporates logic and physical designtools such as HDL compilers and simulation model build tools to processdesign structure 920 together with some or all of the depictedsupporting data structures along with any additional mechanical designor data (if applicable), to generate a second design structure 990.

Design structure 990 resides on a storage medium or programmable gatearray in a data format used for the exchange of data of mechanicaldevices and structures (e.g. information stored in a IGES, DXF,Parasolid XT, JT, DRG, or any other suitable format for storing orrendering such mechanical design structures). Similar to designstructure 920, design structure 990 preferably comprises one or morefiles, data structures, or other computer-encoded data or instructionsthat reside on transmission or data storage media and that whenprocessed by an ECAD system generate a logically or otherwisefunctionally equivalent form of one or more of the embodiments of theinvention shown in FIGS. 1-11. In one embodiment, design structure 990may comprise a compiled, executable HDL simulation model thatfunctionally simulates the devices shown in FIGS. 1-11.

Design structure 990 may also employ a data format used for the exchangeof layout data of integrated circuits and/or symbolic data format (e.g.information stored in a GDSII (GDS2), GL1, OASIS, map files, or anyother suitable format for storing such design data structures). Designstructure 990 may comprise information such as, for example, symbolicdata, map files, test data files, design content files, manufacturingdata, layout parameters, wires, levels of metal, vias, shapes, data forrouting through the manufacturing line, and any other data required by amanufacturer or other designer/developer to produce a device orstructure as described above and shown in FIGS. 1-11. Design structure990 may then proceed to a stage 995 where, for example, design structure990: proceeds to tape-out, is released to manufacturing, is released toa mask house, is sent to another design house, is sent back to thecustomer, etc.

The methods as described above are used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed:
 1. A structure, comprising: a plurality of deep trenchcapacitors formed in a silicon on insulator (SOI) substrate, each of theplurality of deep trench capacitors having a fin structure includingepitaxial material comprising semiconductor material over exposedsidewalls of fin structures and semiconductor material of SOI fins eachof which have ends in contact with respective fin structures of the deeptrench capacitors.
 2. The structure of claim 1, wherein the epitaxialmaterial is on ends of the SOI fins and ends of the fin structures ofthe deep trench capacitors
 3. The structure of claim 1, wherein thesemiconductor material is silicon.
 4. The structure of claim 1, whereinthe fin structures are polysilicon fins formed in contact with the SOIfins, and ends of the SOI fins are connected to respective polysiliconfins.
 5. The structure of claim 1, wherein the ends of the SOI finscontact ends of the fin structures of the deep trench capacitors in alongitudinal direction.
 6. The structure of claim 5, wherein theepitaxial material comprises silicon at a depth of about 15 nm to 25 nmto reduce strap resistance and make a robust connection between theplurality of SOI fins and the respective fin structures of the deeptrench capacitors.
 7. The structure of claim 1, further comprising agate structure extending over an insulator material and the SOI fins,the gate structure comprises a gate dielectric material over the SOIfins, another semiconductor material over the gate dielectric material,and a capping material over the another semiconductor material.
 8. Thestructure of claim 7, wherein the gate dielectric material is one ofhafnium oxide and SiO₂, the another semiconductor material is silicon,and the capping material is nickel.
 9. The structure of claim 8, whereinthe another semiconductor material is insulated from the polysiliconfins by an oxide material to prevent shorts in the deep trenchcapacitors.
 10. The structure of claim 9, further comprising sidewallson the gate structure.
 11. The structure of claim 10, wherein thesidewalls on the gate structure comprise nitride material.
 12. Thestructure of claim 10, wherein the sidewalls on the gate structurecomprise oxide material.
 13. The structure of claim 1, wherein the endsof the SOI fins and the ends of the fin structures of the deep trenchcapacitors are longitudinal ends.